Drying in Peru: the Final Step in Quality Improvement
The final step in post-harvest processing needs to be considered as important as all the steps leading up to it in producing a high quality and consistent final product. As a specialty coffee exporter, we often make the question: how can we know that a coffee that tastes great before export will still taste great when it is roasted and served on the other side of the world months later? Science is telling us more and more that the ability of a great coffee to keep tasting great months after arrival, comes from how that coffee was dried.
5 Minutes Read
By Ben Schweizer
Former Peru Country Manager
When I worked as a roaster and green coffee buyer in the USA, I cupped many and purchased a few Peruvian coffees in the hope of showcasing an origin that I felt had all the potential to produce great coffee. Unfortunately, my experiences with these Peruvian ¨specialty¨ lots was disappointing, and I came to agree with the sentiment of most of my roasting peers: that even the best Peruvian coffees which cup well when fresh, quickly lose vibrancy and turn woody. I always wondered what makes initially great-tasting coffees lose flavor so rapidly? Even in humidity and temperature-controlled conditions these coffees deteriorate rapidly and lose what made them ¨specialty coffees¨ in the first place.
I have now been working in the field cupping, talking with farmers, and getting to know the intricacies of coffee production in Peru for almost a year. My personal goal and the goal of Caravela Peru is to source and export coffee that will prove this prevailing reputation of Peruvian specialty coffee wrong. The key question is: how can we know that a coffee that tastes great before export will still taste great when it is roasted and served on the other side of the world months later? Science is telling us more and more that the ability of a great coffee to keep tasting great months after arrival, comes from how that coffee was dried.
Common Drying Practices in Peru
We now know that beans dried gradually, consistently, and without exposure to extreme heat will produce coffee that tastes better before and after export. The issue is that coffee producers are under constant financial pressure to make the post-harvest process as efficient as possible in order to sell their product quickly, so as to have access to cash flow to continue financing their harvest. Cooperatives are also under pressure to dry coffee as quickly as possible in order to get paid at the moment of export to recuperate the money paid to farmers to secure the coffee in the first place.
In Peru this results in the use of concrete patios, drying machines, and most inconsistent of all, drying coffee by placing the pergamino directly on black polypropylene sheets laid out on the ground to dry under full sun. The problem is that these drying methods shock the coffee, drying it too quickly. If coffee is dried rapidly with high heat the first damage occurs when the embryo in the coffee seed dies. At this point the coffee stops developing flavors and so doesn’t reach its highest potential. Under direct sun and high heat the natural protective pergamino layer of the coffee tears open, exposing the green coffee bean within. Finally, coffees dried using these methods do not result in consistent humidity levels from bean to bean.
Imagine: all the coffee beans within a bag of coffee may have a humidity reading of 11%, but half the beans may be too humid at 13% and the other half too dry at 9%. In time those water molecules will move from the wetter beans and naturally be sucked up by the drier beans, and that movement of water molecules, or water activity, damages quality. But why is this a problem?
The problem is that this movement of water molecules weakens the cell walls of the endosperm which makes up the green flesh of the coffee bean. And when these cell walls weaken, the delicious natural oils that they hold inside are exposed to the air, and that oil oxidizes, losing it’s ¨special¨ flavors.
Water Activity as a Lens Into Drying Quality
Many farmers and producers are just beginning to learn what ¨water activity¨ is, but it is exactly that: a look at how much activity, or movement of water molecules, is occurring within a bag of coffee. Less movement of water molecules means that the beans are already more or less all the same level of humidity and the water doesn’t have to move around to reach equilibrium. This is why we test for water activity: it gives us a lens into the drying methods applied to a lot of coffee. We can determine if it was dried gradually and consistently resulting in a bag of coffee where every single bean is stable in humidity, and the humidity of each individual bean is consistent with the rest of the beans within the lot.
For the specialty coffee community to be able to taste the vibrancy of the finest Peruvian coffees, those coffees must be dried with a consistent drying rate at temperatures below 35 degrees Celsius. A gradual and consistent drying curve is the only way to guarantee even drying among the beans as well as within each individual green coffee bean. Slow drying means the water molecules migrate more slowly throughout the cellulose of the green bean without rupturing the cell walls of the coffee, thus protecting the essential oils that give coffee its unique flavor from oxidation.
“For the specialty coffee community to be able to taste the vibrancy of the finest Peruvian coffees, those coffees must be dried with a consistent drying rate at temperatures below 35 degrees Celsius.”
Caravela’s Mission to Educate Producers and Improve Drying Practices
For all these reasons, our PECA team is working hard to educate farmers so that the final and longest step in their production process still has a great effect on the ultimate quality of their coffee. More gradual drying methods such as African and parabolic drying beds require much more investment in materials and construction than patio drying, but ultimately the benefits in the resulting quality justify the cost. By providing technical support to advise farmers on the most impactful ways to invest in their farms, as well as providing these farmers with excellent prices for coffees dried in a gradual and consistent manner, we hope to be able to spread the message that the best coffee should only ever be dried ¨DESPACITO¨.
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